Author: Shiow-Jing Huang

Publisher:

Published: 2012

Total Pages: 123

ISBN-13:

The study of CO2 reduction to produce C{u2010}C bond and hydrogenated carbon bonds as the final product has been discussed for the past decade (methane, ethane, etc). The C{u2010}C bond and hydrogenated carbon can be used as a high value energy source and for chemical feedstocks. The long{u2010}term goal of this research is to be able to take abundant CO2 and electrochemically reduce it to a useful energy source or chemical feedstock using renewable electric energy sources. A comprehensive review of electrochemical CO2 reduction has been performed, and there are numerous literature references for many different metal electrocatalyst, and in general it is concluded that copper is most active surface for CO2 reduction. In the mechanism of CO2 reduction, the step involving CO(ads)as an intermediate is key, then this intermediate reacts to form C{u2010}C bonds as a final product. Therefore we wanted to explore this reaction further on controlled copper layers on metal substrates as an approach to modify the copper surface energetics towards reactant adsorption and stabilization of reaction of intermediates on the surface. Underpotential deposition of copper adlayers is a highly promising technique for modification of a substrate surface such as Pt and Au (among others) of either bulk disk electrodes or supported nanoparticle electrocatalyst, and it has been explored for synthesizing shell{u2010}core electrocatalyst to promote the oxygen reduction reaction (ORR). However, underpotential deposition of copper has not been studied for CO2 reduction. Since the preparation of these upd layers involves deposition in one electrolyte (acid) and electrochemical reduction of CO2 in another electrolyte (neutral), it was unclear that these electrocatalyst could be prepared and maintained stable while transferring electrolytes for electrocatalyst studies (copper easily oxidizes in air). This research set out to demonstrate that a Cuupd film on a Pt or Au substrate (macro size disk electrodes or carbon supported precious metal nanoparticles) will be uniform and stable after preparation and through transfer to a CO2 reduction electrolyte for a CO2 reduction experiment. This was shown to be the case by using voltammetric stripping, by carrying out Pt displacement reactions, and by xps studies. Furthermore, we have observed voltammetric reduction currents similar to the literature for copper electrodes suggesting the key intermediate of CO adsorption. After the CO2 testing, the Cuupd was observed to still be present as one monolayer of Cu on the substrate surface. We conclude that we can experimentally prepare Cuupd layers on both macro size and nanoparticles of Au and Pt electrodes, and that we can indeed maintain a stable monolayer for carrying out CO2 reduction experiment after transferring electrolytes.